It is sometimes desired to provide reagent to a remote reaction zone such as at a specific location within the interior of a furnace. For example, in reburning wherein hydrocarbon radicals convert NOx to nitrogen gas for pollution control purposes, it is desired to provide hydrocarbon fuel such as natural gas or coal, which serves as a source of hydrocarbon radicals, to a remote area which contains flue gas. In another example it may be desired to provide ammonia or urea deep within a furnace to react with the NOx to form nitrogen gas.
One way to accomplish such reagent provision is to pass the reagent to the remote reaction zone using a long lance or other long provision means, but this is complicated to carry out and would require frequent replacement of the lance if the reaction zone were associated with a hot or corrosive environment such as a furnace. Another way to deliver reagents to a specific location in the boiler or furnace is to use. high velocity jets which typically penetrate deep into an enclosure before mixing is complete. However, this approach can lead to significant increases in the formation of pollutants in burners, such as NOx, and consumption of reagent prior to reaching the reaction zone. Both effects are due to the high entrainment rates characteristic of turbulent jets. Further, the high entrainment rates lead to recirculation of hot flue gas, which can contain particulate or corrosive gases, to the boiler or furnace wall, exacerbating deposition on the wall and corrosion. Yet another method is through the use of computational fluid dynamics modeling of a reaction zone such as a furnace environment. In this method detailed calculations are made to describe the furnace environment and nozzles or lances can then be placed in appropriate locations. This method can be effective but is quite complex to execute.
Accordingly, it is an object of this invention to provide a method whereby reagent may be provided to a reaction zone which is separated by a distance from the point where the reagent passes out from the injection device.